1. Field of the Invention
The present invention relates in general to a method of detecting an abnormality of an R/D converter. In particular, the present invention aims at constructing an inexpensive and simple failsafe system by installing an abnormality detection/self-diagnosis function in an R/D converter to integrate abnormality detection means, which is conventionally provided in an external circuit other than a resolver apparatus, with the resolver apparatus.
2. Description of the Related Art
For a resolver/digital (R/D) converter for carrying out R/D conversion of a resolver which is conventionally used, for example, there is a method including converting an analog signal into a digital signal. This method is described in JP 3,442,316B and U.S. Pat. No. 6,278,388. In this case, most of the failsafe functions such as detecting various abnormalities rely on an external circuit other than a resolver apparatus (a combination of a resolver with an R/D converter), or a host arithmetic and logic unit such as a microcomputer.
In addition, as for a method including detecting disconnection of a resolver, a method described in JP 2000-131096 A can be given as an example.
Since the conventional resolver apparatus is configured in a manner as described above, it has the following problem existing therein.
That is, since the function such as detecting an abnormality of the R/D converter is not complete, the external circuit other than the resolver apparatus, or the host system such as a microcomputer must be used for the abnormality detecting function for realizing the failsafe. As a result, the conventional resolver apparatus is complicated and expensive.